The ocular pressure of an eye may be measured by a procedure using an applanation tonometer. A commonly used applanation tonometer is described in U.S. Pat. No. 3,070,997. According to the procedure, a planar applanating surface on a prism of the applanation tonometer is brought into contact with a cornea of an eye. The tonometer is adjusted until the surface of the cornea conforms substantially with the planar applanating surface and then a measurement is taken. Due to the applanating surface contacting the eye, the applanating surface is exposed to lacrimal fluid from the eye. The contamination of the applanating surface with the lacrimal fluid has been recognized as posing a risk of transmission of disease. Thus, the applanating surface should be disinfected between each use to prevent transmitting lacrimal fluid from one eye to another.
Prior methods for disinfecting the applanating surface require modification of the tonometer for installation of a disinfecting system or dismantling of the prism from the tonometer between each use.